It may be due to the importance of nutrients in crop production ?

Hi,

PSBs have variable phosphatases, some have phytases and some can break C-P bonds, also they are able to secrete organic acids that contribute towards solubiization of rock and other insoluble phosphates. 

As said earlier, rock phosphates and guano (excretions of sea birds) are limited and are not renewable, so there is the need to harness the potential of PSBs compared to say N-fixers.

It is even important to find suitable ways of using phytate which is contributed by decaying plant material and animal poop. 

Many plants are also highly dependent on phosphate, example Azolla. Therefore, PSBs are more important than N-fixers for some plants. 

Also, in Sri Lanka, we have a lot of appetite and therefore, PSBs with other films are popular additives to the soil. 

Hope this helps.

Best Wishes

Dilantha

Dear Dr.Meena

N fixers have been in use since long time and they will continue to be used in future also.As I understand the volume of N fixing biofertilizers use is more than P  solubilizers. P solubilizers are equally important as global  P reserves especially in some countries like India are limited.P solubilizers can solubilise both insoluble P in soil and the P accumulated from regular fertilizer additions.So it helps to utilize the residual P in soil very efficiently.The Usefulness of K solubilizing bio- fertilizers is questionable as the soil nonexchangeable K can be utilized by plants without much difficulty and also the mechanism, the source and the magnitude of K solubilized are questionable.

Dear Dr.Meena,

It's a very good question about the reflection on soil-plant-nutrient research. In my point of view, as a researcher, PSB-KSB or N-fixers should be important at the same level because these nutrients are vital for crop production even if the quantity that require by crop is different. The level can change depending on the quantity of such nutrient in soil and what nutrient that we have to improve for example in low P soil, PSB should be the most important. The number of publication of PSB increase because P becomes scare (See Cordell Dana publications). I think the research of Cordell et al attracts the attention of scientific community on P research (also for PSM research) then P become a hot subjet. However, I think , as a researcher, we have to keep in mind that all nutrients are importants for crop and these are dynamique in time and space. They are also interacted with soil-soil organisms-plant system. The important of such nutrient could be consider depending on soil nutrient status and what we have to improve for increasing crop production.

 Generally in India, the environmental conditions and soil reaction plays major role in non availability of P. Nitrogenous fertilizers and N fixers are used widely and indiscriminately to boost vegetative growth by farming community (E.g. Urea in rice). Pertaining to K, which is high in Indian soils in general. Like N, the atmosphere does not provide phosphorus. Instead, orthophosphates originate largely from primary and secondary minerals and/or from organic sources. However, the phosphorus cycle is by no means less complex than the nitrogen cycle, and there are many factors that affect the availability of phosphorus in the soil including abiotic factors and soil pH. In alkaline pH, P is fixed in the soil and hence PSBs are used to make them available. Because, plant roots absorb phosphorus from the soil solution. In comparison to other macronutrients, the phosphorus concentration in the soil solution is much lower and ranges from 0.001 mg/L to 1 mg/L (Brady and Weil, 2002). In general, roots absorb phosphorus in the form of orthophosphate, but can also absorb certain forms of organic phosphorus. Phosphorus moves to the root surface through diffusion.

Thanking you so much for your views

Dear Meena,

We have already applied a lot of phosphorus in the soil which has been transformed to unavailable form due to various reasons. The key to open this P Locker is PSB and moreover we are importing a lot of phosphatic fertilizers from other countries. That is why PSB is very popular.